Bull polishing, bulling, spit polishing or spit shining refers to a method for polishing leather products in such a way as to give an extremely high shine effect. It is commonly used in the military as a traditional method of presenting leather accessories (such as a Sam Browne belt) and boots for inspection. The finished effect should leave the surface of the leather as reflective as a mirror.
There is great debate as to the best method for bull polishing, to a point where a 'lore' may be said to exist. Among techniques advocated are melting the polish, the addition of cigar ash to the polish, and substituting coffee for water or spit. However, the basic principles remain the same:
Wear the item a few times to establish any natural creases that occur during use. This is particularly important if the leather has been "burnt down" with beeswax (a process that gives the leather a smoother finish).
Polish the item in the normal way with a brush a few times to get a decent 'regular' polish.
Apply thin layers of polish to the item in small circular motions with a cloth (e.g. a yellow duster) until a dull, smooth shine appears.
Polish the final layer of polish with the damp cloth or cotton wool until the desired shine appears.
Use little amounts of water, keep the shoe rag damp.
Do not use too much polish, it will take a long time to polish and it doesn't give a very good shine.
Ultimately, the process involves polishing the applied thin layers of polish, not the leather itself. The process can be lengthy and is best learned with practice. The down side to this method is that the slightest touch to the laminated layers of brittle dry polish could end up with them cracking or even shattering like glass or even the leather breaking up as the nourishment supplied by the oils in the polish never actually reached the leather.